Power amplification module for multiple bands and multiple standards

ABSTRACT

Provided is a communication unit that includes first and second power-amplification modules, which can be integrated. The first power-amplification module includes a first power-amplifier for a first frequency band in a first communication scheme, a second power-amplifier for a second frequency band in the first communication scheme, a third power-amplifier for a third frequency band in a second communication scheme, a fourth power-amplifier for a fourth frequency band in the second communication scheme, a first bias circuit that generates a first bias current to the first and second power-amplifiers, and a bias current circuit that converts the first bias current into a second bias current to the third and fourth power-amplifiers. The second power-amplification module includes a fifth power-amplifier for a fifth frequency band in the first communication scheme, and a second bias circuit that generates a third bias current to the fifth power-amplifier.

This is a continuation of U.S. application Ser. No. 15/082,567 filed onMar. 28, 2016 which claims priority from Japanese Patent Application No.2015-125868 filed on Jun. 23, 2015. The contents of these applicationsare incorporated herein by reference in their entireties.

BACKGROUND OF THE DISCLOSURE

Field of the Disclosure

The present disclosure relates to a communication unit.

Description of the Related Art

A communication unit that includes a power amplification module foramplifying the power of a radio frequency (RF) signal that is to betransmitted to a base station is employed in a portable terminal thatutilizes a cellular phone communication network. In recent years, thenumber of users of portable terminals has increased tremendously and thenumber of frequency bands utilized by cellular phones has increased inorder to handle the communication traffic created by these users.Therefore, it is required that portable terminals support thesefrequency bands.

In addition, from the viewpoints of design restrictions, profilereduction and size reduction of portable terminals, it is required thatsuch communication units be reduced in size. Accordingly, for example, apower amplification module is used in which a plurality of poweramplifiers, which support a plurality of communication schemes (modes)and a plurality of frequency bands, are integrated into a single module,as described in “TQM7M9050 data sheet”, TriQuint Corp., (online), webaddress: www.triquint.com/products/d/DOC-B-00000332.

The power amplification module disclosed in “TQM7M9050 data sheet”,TriQuint Corp., (online), web address:www.triquint.com/products/d/DOC-B-00000332 supports the secondgeneration mobile communication system (2G) and the third/fourthgeneration mobile communication system (3G/4G). This power amplificationmodule includes a power amplifier for a low frequency band (LB) that isa 1 GHz band of the global system for mobile communications (GSM)(registered trademark), which is the 2G communication standard, a poweramplifier for a high frequency band (HB) that is a 2 GHz band of GSM, apower amplifier for an LB that is a 1 GHz band of 3G/4G and a poweramplifier for an HB that is a 2 GHz band of 3G/4G.

In this power amplification module, the 3G/4G LB power amplifier coverstwo frequency bands that are band 5 (B5: transmission frequency band of824 MHz to 849 MHz) and band 8 (B8: transmission frequency band of 880MHz to 915 MHz). In addition, the 3G/4G HB power amplifier covers fourfrequency bands that are band 1 (B1: transmission frequency band of 1920MHz to 1980 MHz), band 2 (B2: transmission frequency band of 1850 MHz to1910 MHz), band 3 (B3: transmission frequency band of 1710 MHz to 1785MHz) and band 4 (B4: transmission frequency band of 1710 MHz to 1755MHz).

In recent years, as a technique for improving the downlink communicationspeed from a base station to a portable terminal, downlink carrieraggregation (hereafter, “DLCA”), which is a technique in which aplurality of frequency bands are simultaneously used in the downlink hasbeen focused upon in long term evolution (LTE) advanced, which is a 4Gcommunication standard. Consequently, a communication unit that issuitable for downlink carrier aggregation has been demanded.

BRIEF SUMMARY OF THE DISCLOSURE

The present disclosure has been made in light of the above-describedcircumstances and it is an object thereof to provide a multi-modemulti-band communication unit that is suitable for downlink carrieraggregation.

A communication unit according to a preferred embodiment of the presentdisclosure includes first and second power amplification modules thatare each integrated so as to be separate from each other. The firstpower amplification module includes a first power amplifier thatamplifies a first transmission signal of first frequency band in a firstcommunication scheme, a second power amplifier that amplifies a secondtransmission signal of a second frequency band, which is lower than thefirst frequency band, in the first communication scheme, a third poweramplifier that amplifies a third transmission signal of a thirdfrequency band in a second communication scheme, a fourth poweramplifier that amplifies a fourth transmission signal of a fourthfrequency band, which is lower than the third frequency band, in thesecond communication scheme, a first bias current generating circuitthat generates a first bias current to be supplied to the first andsecond power amplifiers, and a bias current converting circuit thatconverts the first bias current into a second bias current to besupplied to the third and fourth power amplifiers. The second poweramplification module includes a fifth power amplifier that amplifies afifth transmission signal of a fifth frequency band, which is lower thanthe second frequency band, in the first communication scheme, and asecond bias current generating circuit that generates a third biascurrent to be supplied to the fifth power amplifier.

According to the preferred embodiment of the present disclosure, amulti-mode multi-band communication unit that is suitable for downlinkcarrier aggregation is provided.

Other features, elements, characteristics and advantages of the presentdisclosure will become more apparent from the following detaileddescription of preferred embodiments of the present disclosure withreference to the attached drawings.

BRIEF DESCRIPTION THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates an example configuration of a communication unitaccording to an embodiment of the present disclosure;

FIG. 2 illustrates an example of the configurations of poweramplification modules;

FIG. 3 illustrates an example of the configuration of a front endcircuit;

FIG. 4A illustrates an example of a situation in which signalinterference occurs in DLCA;

FIG. 4B illustrates another example of a situation in which signalinterference occurs in DLCA;

FIG. 5 lists combinations of frequency bands where a reception signalexperiences interference from a transmission signal in DLCA;

FIG. 6 illustrates an example configuration of a transmission unit forexplaining the effect of coupling between terminals of a poweramplification module; and

FIG. 7 illustrates another example configuration of a transmission unitfor explaining the effect of coupling between terminals of a poweramplification module.

DETAILED DESCRIPTION OF THE DISCLOSURE

Hereafter, an embodiment of the present disclosure will be describedwhile referring to the drawings. FIG. 1 illustrates an exampleconfiguration of a communication unit 100 according to an embodiment ofthe present disclosure. The communication unit 100 is for example usedto perform transmission and reception, in a mobile communication devicesuch as a cellular phone, of various signals such as speech and data toand from a base station. The communication unit 100 supports a pluralityof communication schemes (multiple modes). Specifically, thecommunication unit 100 supports 3G/4G (first communication scheme) and2G (second communication scheme). In addition, the communication unit100 supports a plurality of frequency bands (multiple bands) among radiofrequencies (RF). Furthermore, the communication unit 100 supports DLCA.

As illustrated in FIG. 1, the communication unit 100 includes atransmission circuit 110, a reception circuit 120, power amplificationmodules 130 and 140, a front end circuit 150 and an antenna 160.

The transmission circuit 110 modulates an input signal such as speech ordata on the basis of a modulation scheme such as LTE or GSM and outputsan RF signal in order to perform wireless transmission. The transmissioncircuit 110 can include a plurality of transmission circuits inaccordance with the modulation schemes and frequency bands used.

The reception circuit 120 receives a reception signal (RF signal) outputfrom the front end circuit 150, demodulates the reception signal andoutputs the demodulated reception signal. The reception circuit 120 caninclude a plurality of reception circuits in accordance with themodulation schemes and frequency bands.

The power amplification modules 130 and 140 each amplify the power of aninput RF signal up to the level that is required to transmit the RFsignal to the base station and then output the amplified signal. Thepower amplification module 130 (first power amplification module)amplifies RF signals of a 3G/4G 2.5 GHz band (very high band (VHB)), a3G/4G 2 GHz band (high band (HB)), a 2G 2 GHz band (high band (HB)) anda 2G 1 GHz band (low band (LB)). In addition, the power amplificationmodule 140 (second power amplification module) amplifies RF signals of a3G/4G 1 GHz band (low band (LB)). The power amplification modules 130and 140 will be described in detail later.

The front end circuit 150 switches the paths of transmission signals andreception signals, performs filtering processing and so forth. The frontend circuit 150 will be described in detail later.

FIG. 2 illustrates an example of the configurations of the poweramplification modules 130 and 140. The power amplification modules 130and 140 have each been integrated as a single module.

The power amplification module 130 includes power amplifiers 200A, 200B,200C and 200D, a bias circuit 210A and switch circuits 220A and 220B.

The power amplifier 200A (first power amplifier) amplifies and thenoutputs an RF signal (first transmission signal) input from a terminalVHB IN. The power amplifier 200A supports a 3G/4G 2.5 GHz band (VHB)(first frequency band).

Specifically, the power amplifier 200A supports band 7 (B7: transmissionfrequency band of 2500 to 2570 MHz). In addition, the power amplifier200A supports band 40 (B40: transmission frequency band of 2300 to 2400MHz) and band 41 (B41: transmission frequency band 2496 to 2690 MHz)(first frequency band) used in a time division duplexing (TDD)communication scheme. The frequency bands given here are examples andthe frequency bands supported by the power amplifier 200A are notlimited to these frequency bands.

The power amplifier 200B (second power amplifier) amplifies and thenoutputs an RF signal (second transmission signal) input from a terminalHB_IN. The power amplifier 200B supports a 3G/4G 2 GHz band (HB) (secondfrequency band). Specifically, the power amplifier 200B supports band 1(B1: transmission frequency band of 1920 to 1980 MHz), band 2 (B2:transmission frequency band of 1850 to 1910 MHz), band 3 (B3:transmission frequency band of 1710 to 1785 MHz) and band 4 (B4:transmission frequency band of 1710 to 1755 MHz). In addition, the poweramplifier 200B supports band 34 (B34: transmission frequency band of2010 to 2025 MHz) and band 39 (B39: transmission frequency band of 1880to 1920 MHz) (second frequency band) used in a TDD communication scheme.The frequency bands given here are examples and the frequency bandssupported by the power amplifier 200B are not limited to these frequencybands.

The power amplifier 200C (third power amplifier) amplifies an RF signal(third transmission signal) input from a terminal GSMHB_IN and thenoutputs the amplified signal from a terminal GSMHB_OUT. The poweramplifier 200C supports a 2G GSM 2 GHz band (HB) (third frequency band).

The power amplifier 200D (fourth power amplifier) amplifies an RF signal(fourth transmission signal) input from a terminal GSMLB_IN and thenoutputs the amplified signal from a terminal GSMLB_OUT. The poweramplifier 200D supports a 2G GSM 1 GHz band (LB) (fourth frequencyband).

The power amplifiers 200A, 200B, 200C and 200D may be each formed of aplurality of stages. For example, the power amplifiers 200A and 200B caneach have a two-stage configuration. In addition, the power amplifiers200C and 200D can each have a three-stage configuration, for example.

The bias circuit 210A supplies a bias current having a levelcorresponding to a bias control signal, which is input from the outside,to the power amplifiers 200A, 200B, 200C and 200D. The bias circuit 210Aincludes a bias current generating circuit 230A and a bias currentconverting circuit 231. The bias current generating circuit 230A (firstbias current generating circuit) generates a bias current for the 3G/4Gpower amplifiers 200A and 200B (first bias current). The bias currentgenerating circuit 230A, for example, includes a plurality of currentsources having different current levels and is able to generate a biascurrent by combining the currents from these current sources inaccordance with the bias control signal. The bias current convertingcircuit 231 converts the 3G/4G bias current generated by the biascurrent generating circuit 230A into a 2G bias current (second biascurrent) and supplies the 2G bias current to the 2G power amplifiers200C and 200D.

The switch circuits 220A and 220B switch a signal path in accordancewith a switch control signal input from the outside.

Specifically, the switch circuit 220A (first switch circuit) is able tooutput a signal output from the power amplifier 200A to a terminalB7_OUT, a terminal B40TRx or a terminal B41TRx. The terminal B7_OUT is aterminal for outputting a band 7 signal. In addition, the terminalB40TRx and the terminal B41TRx (first transmission/reception terminals)are terminals for respectively inputting and outputting a band 40 signaland a band 41 signal.

Furthermore, the switch circuit 220A is able to respectively outputsignals input from the terminal B40TRx and the terminal B41TRx to aterminal B40Rx and a terminal B41Rx. The terminal B40Rx and the terminalB41Rx (first output terminals) are terminals that are connected to areception circuit 120 for band 40 and band 41 (first reception circuit).

The switch circuit 220B (second switch circuit) is able to output asignal output from the power amplifier 200B to a terminal B1_OUT, aterminal B2_OUT, a terminal B3 OUT, a terminal B4_OUT or a terminalB34/39TRx. The terminal B1_OUT, the terminal B2_OUT, the terminal B3_OUTand the terminal B4_OUT are terminals for outputting band 1, band 2,band 3 and band 4 signals, respectively. Furthermore, the terminalB34/39TRx (second transmission/reception terminal) is a terminal forinputting and outputting band 34 and band 39 signals.

In addition, the switch circuit 220B is able to output a signal inputfrom the terminal B34/39TRx to a terminal B34/39Rx. The terminalB34/39Rx (second output terminal) is a terminal that is connected to areception circuit 120 for band 34 and band 39 (second receptioncircuit).

The power amplification module 140 includes a power amplifier 200E, abias circuit 210B and a switch circuit 220C.

The power amplifier 200E amplifies and then outputs an RF signal inputfrom a terminal LB_IN. The power amplifier 200E supports a 3G/4G 1 GHzband (LB). Specifically, the power amplifier 200E supports band 5 (B5:transmission frequency band of 824 to 849 MHz), band 8 (B8: transmissionfrequency band of 880 to 915 MHz), band 17 (B17: transmission frequencyband of 704 to 716 MHz), band 20 (B20: transmission frequency band of832 to 862 MHz), band 26 (B26: transmission frequency band of 814 to 849MHz) and band 28 (B28: transmission frequency band of 700 to 748 MHz).The frequency bands given here are examples and the frequency bandssupported by the power amplifier 200E are not limited to these frequencybands.

The power amplifier 200E may be formed of a plurality of stages. Forexample, the power amplifier 200E can have a two-stage configuration.

Similarly to the bias circuit 210A, the bias circuit 210B supplies tothe power amplifier 200E a bias current having a level corresponding toa bias control signal input from the outside. The bias circuit 210Bincludes a bias current generating circuit 230B. The bias currentgenerating circuit 230B generates a bias current for the 3G/4G poweramplifier 200E. Since the power amplification module 140 does notinclude a 2G power amplifier, the bias circuit 210B is not provided witha circuit for converting a 3G/4G bias current into a 2G bias current.

The switch circuit 220C switches a signal path in accordance with aswitch control signal input from the outside. Specifically, the switchcircuit 220C is able to output a signal output from the power amplifier200E to a terminal B5/B26_OUT, a terminal B8_OUT, a terminal B17_OUT, aterminal B20_OUT or a terminal B28_OUT. The terminal B5/B26_OUT, theterminal B8_OUT, the terminal B17_OUT, the terminal B20_OUT and theterminal B28_OUT are terminals for outputting band 5/band 26, band 8,band 17, band 20 and band 28 signals, respectively.

FIG. 3 illustrates an example of the configuration of the front endcircuit 150. As illustrated in FIG. 3, the front end circuit 150includes duplexers 300 (300 x and 300 y), a switch circuit 310 and adiplexer 320.

Two power amplifiers 200 x and 200 y and two reception circuits 120 xand 120 y are illustrated in FIG. 3. The power amplifier 200 x and thereception circuit 120 x support a band x (Bx). The power amplifier 200 yand the reception circuit 120 y support a band y (By).

The duplexer 300 x supports band x. The duplexer 300 x outputs to theswitch circuit 310 a transmission signal of band x output from the poweramplifier 200 x. In addition, the duplexer 300 x outputs to thereception circuit 120 x a reception signal of band x output from theswitch circuit 310. The duplexer 300 x is for example formed using a lowpass filter (LPF), a band pass filter (BPF) or the like.

The duplexer 300 y supports band y. The duplexer 300 y outputs to theswitch circuit 310 a transmission signal of band y output from the poweramplifier 200 y. In addition, the duplexer 300 y outputs to thereception circuit 120 y a reception signal of band y output from theswitch circuit 310. The duplexer 300 y is for example formed using a lowpass filter (LPF), a band pass filter (BPF) or the like.

The switch circuit 310 switches a signal path between the diplexer 320and the duplexers 300 x and 300 y in accordance with the frequency bandof a transmission or reception signal.

The diplexer 320 divides a reception signal from the antenna 160 intoreception signals of the respective frequency bands and combinestransmission signals of a plurality of frequency bands. The diplexer 320is for example formed using a low pass filter (LPF), a high pass filter(HPF) or the like.

Although a circuit that supports two frequency bands is illustrated inFIG. 3 in order to simplify the description, the configuration of thecommunication unit 100 is not limited to this. In addition, the frontend circuit 150 may include other filter circuits and so forth inaccordance with the supported frequency bands.

Next, description will be given of signal interference inside thecommunication unit 100 in the case where DLCA is performed.

First, the principle behind signal interference in DLCA will bedescribed.

FIG. 4A illustrates an example of a situation in which signalinterference occurs in DLCA. In the example illustrated in FIG. 4A, twofrequency bands BAND_A and BAND_B are used. The lower frequency bandBAND_A is used in uplink. Here, fTX_A denotes a transmission frequencyin the frequency band BAND_A, fRX-A denotes a reception frequency in thefrequency band BAND_A and fRX_B denotes a reception frequency in thefrequency band BAND B.

In the example illustrated in FIG. 4A, if an integer multiple of thetransmission frequency (nfTX_A) is substantially equal to the receptionfrequency (fRX_B) in the frequency band BAND_B, the reception signalwill experience interference from a harmonic signal and the receptionsignal sensitivity will be reduced.

FIG. 4B illustrates another example of a situation in which signalinterference occurs in DLCA. In the example illustrated in FIG. 4B, twofrequency bands BAND_A and BAND_B are used. The higher frequency bandBAND_B is used in uplink. Here, fRX_A denotes a reception frequency inthe frequency band BAND_A, fTX-B denotes a transmission frequency in thefrequency band BAND_B and fRX_B denotes a reception frequency in thefrequency band BAND_B.

In the example illustrated in FIG. 4B, if the reciprocal of an integermultiple of the transmission frequency ((1/n)fTX_A) is substantiallyequal to the reception frequency (fRX_A) in the frequency band BAND_A,the reception signal will experience interference from the transmissionsignal and the reception signal sensitivity will be reduced.

Description will be given of the mechanism behind the reduction in thereception signal sensitivity in the example illustrated in FIG. 4B. Adirect conversion method, which is suitable for integration, iscurrently applied to the reception circuits of cellular phones. In thismethod, the center frequency of a reception signal and a localoscillation frequency applied to a mixer are the same. In order toprovide an adequate signal-to-noise ratio, a large signal is used as thelocal oscillation signal and the local oscillation signal has a largeharmonic component. In the example illustrated in FIG. 4B, the harmonicfrequency is n times the reception frequency (fRX_A). If an input signalof this harmonic frequency is applied to the reception circuit, theinput signal will undergo frequency conversion by a harmonic of thelocal oscillation signal and become an in-band interference wave. Thus,the reception signal sensitivity will be reduced.

As illustrated in FIGS. 4A and 4B, in the case where DLCA is performed,when a specific relationship holds true between the two frequency bands,the reception signal experiences interference from the transmissionsignal and the reception sensitivity is reduced.

FIG. 5 lists the combinations of frequency bands having this specificrelationship. In FIG. 5, “band (DLCA)” indicates the frequency bandsused in DLCA. In addition, “UL” indicates the frequency band of thetransmission signal in the case where DLCA is performed. “Affected DL”indicates the frequency band of a reception signal that experiencesinterference from a transmission signal in the case where thetransmission signal is transmitted in the frequency band indicated by“UL”. For example, if the frequency band of the transmission signal isband 6 (LB) in the case where the frequency bands used in DLCA are band6 and band 7, the reception signal of band 7 (VHB) is affected. Lookingat FIG. 5, the combinations of frequency bands having the specificrelationship are LB and VHB or LB and HB. In contrast, the specificrelationship does not occur for a combination of HB and VHB.

Next, the effect of coupling between terminals of a power amplificationmodule in the case where DLCA is performed will be described.

FIG. 6 illustrates an example configuration of a transmission unit forexplaining the effect of coupling between terminals of a poweramplification module. The transmission unit illustrated in FIG. 6includes a power amplification module 600, duplexers 300, a switchcircuit 310, a low pass filter (LPF) 620, a diplexer 320, an antenna 160and a reception circuit 630.

The power amplification module 600 is an integrated circuit thatincludes power amplifiers 610, 611, 612 and 613. The power amplifiers610, 611, 612 and 613 support band 17, GSM LB, GSM HB and band 4,respectively. The power amplification module 600 is to be used fordescriptive purposes and is different from the power amplificationmodules 130 and 140 of this embodiment.

The duplexers 300 include band pass filters (BPFs) and low pass filters(LPFs) that support band 17, GSM LB, GSM HB and band 4.

The switch circuit 310 includes switches for switching signal pathsbetween the duplexer 300 and the diplexer 320.

The low pass filter (LPF) 620 is provided between the switch circuit 310and the diplexer 320 as a band 17 filter.

The reception circuit 630 is a reception circuit for band 4. Thereception circuits for other frequency bands are not illustrated in FIG.6 in order to simplify the illustration.

The effect of coupling between terminals of the power amplificationmodule 600 will be described for the case where DLCA is performed usingband 17 and band 4 and the frequency band of the transmission signal isband 17 in the configuration illustrated in FIG. 6. A frequency that isthree times the frequency of the transmission signal of band 17 issubstantially equal to the frequency of the reception signal of band 4.

The level of a harmonic signal having a frequency that is three timesthe frequency of the transmission signal of band 17 is −20 dBm at theoutput terminal of the power amplifier 610 for band 17. In addition, theout-of-band suppression of the band pass filters (BPFs) of the duplexers300 is −30 dB, the out-of-band suppression of the low pass filters(LPFs) of the duplexers 300 is −20 dB, the attenuation of the low passfilter (LPF) 620 for band 17 is −30 dB, the out-of-band attenuation ofthe diplexer 320 is −30 dB, the attenuation when the switches of theswitch circuit 310 are on is 0 dB, the attenuation when the switches areoff is −20 dB and the attenuation caused by signal transmission betweenterminals of the power amplification module 600 is −30 dB.

Under these assumptions, the effect of a band 17 transmission signal ofon the reception circuit 630 will be described.

First, a signal path A illustrated in FIG. 6 will be considered. Aharmonic signal is attenuated by −30 dB by the band pass filter (BPF)for band 17 transmission. Next, the harmonic signal passes through aswitch that is in an on state without being attenuated and is thenattenuated by −30 dB by the low pass filter (LPF) for band 17. Then, theharmonic signal is further attenuated by −30 dB by the diplexer 320.Since the switch for band 4 is on, the harmonic signal passes throughthe switch with an attenuation of 0 dB. Then, since the frequency of theharmonic signal is inside the band 4 reception band, the harmonic signalpasses through the band 4 reception band pass filter (BPF) with anattenuation of 0 dB. As a result, the harmonic signal that has passedalong the signal path A acts as an in-band interference signal of −110dBm at the input of the band 4 reception circuit 630.

Next, a signal path B illustrated in FIG. 6 will be considered. Aharmonic signal of the band 17 transmission signal is transmitted to theoutput terminal of the GSM LB power amplifier 611 with an attenuation of−30 dB. The harmonic signal is attenuated by −20 dB by the GSM LBtransmission low pass filter (LPF). Next, the harmonic signal isattenuated by −20 dB by the switch that is in an off state. Then, theharmonic signal is further attenuated by −30 dB by the diplexer 320.Since the switch for band 4 is on, the harmonic signal is not attenuatedby the switch. Then, since the frequency of the harmonic signal isinside the band 4 reception band, the harmonic signal is not attenuatedby the band 4 reception band pass filter (BPF). As a result, theharmonic signal that has passed along the signal path B acts as anin-band interference signal of −110 dBm at the input of the band 4reception circuit 630.

Next, a signal path C illustrated in FIG. 6 will be considered. Aharmonic signal of the band 17 transmission signal is transmitted to theoutput terminal of the GSM HB power amplifier 612 with an attenuation of−30 dB. The harmonic signal has a frequency inside the GSM HB andtherefore is not attenuated by the GSM HB transmission low pass filter(LPF). Next, the harmonic signal is attenuated by −20 dB by the switchthat is in an off state. The harmonic signal does not pass through thediplexer 320 and passes through the band 4 switch without beingattenuated. Then, since the frequency of the harmonic signal is insidethe band 4 reception band, the harmonic signal is not attenuated by theband 4 reception band pass filter (BPF). As a result, the harmonicsignal that has passed along the signal path C acts as an in-bandinterference signal of −70 dBm at the input of the band 4 receptioncircuit 630.

Finally, a signal path D illustrated in FIG. 6 will be considered. Aharmonic signal of the band 17 transmission signal is transmitted to theoutput terminal of the band 4 power amplifier 613 with an attenuation of−30 dB. The harmonic signal is attenuated by −30 dB by the band passfilter (BPF) for band 4 transmission. Then, the harmonic signal passesthrough the band 4 reception band pass filter (BPF) without beingattenuated since the frequency of the harmonic signal is inside the bandand the harmonic signal does not pass through the band 4 switch. As aresult, the harmonic signal that has passed along the signal path D actsan in-band interference signal of −80 dBm at the input of the band 4reception circuit 630.

According to the results illustrated in FIG. 6, the output terminal ofthe GSM HB power amplifier 612 and the output terminal of the band 4(HB) power amplifier 613 are highly sensitive to coupling with theoutput terminal of the band 17 (LB) power amplifier 610. Therefore, itis highly necessary that isolation from the 3G/4G LB power amplifier bestrengthened for the GSM HB power amplifier and the 3G/4G HB poweramplifier.

FIG. 7 illustrates another example configuration of a transmission unitfor explaining the effect of coupling between terminals of a poweramplification module. The transmission unit illustrated in FIG. 7includes a power amplification module 700, duplexers 300, a switchcircuit 310, a low pass filter (LPF) 720, a diplexer 320, an antenna 160and a reception circuit 730.

The power amplification module 700 is an integrated circuit thatincludes power amplifiers 710, 711, 712 and 713. The power amplifiers710, 711, 712 and 713 support band 4, GSM HB, GSM LB and band 5,respectively. The power amplification module 700 is to be used fordescriptive purposes and is different from the power amplificationmodules 130 and 140 of this embodiment.

The low pass filter (LPF) 720 is provided between the switch circuit 310and the diplexer 320 as a band 5 filter.

The reception circuit 730 is a band 5 reception circuit. The receptioncircuits of other frequency bands are not illustrated in FIG. 7 in orderto simplify the illustration.

The effect of coupling between terminals of the power amplificationmodule 700 will be described for the case where DLCA is performed usingband 4 and band 5 and the transmission signal frequency band is band 4in the configuration illustrated in FIG. 7. A frequency that is half thefrequency of the transmission signal of band 4 is substantially equal tothe frequency of the reception signal of band 5. In other words, afrequency that is two times that of the reception signal of band 5 isinside the transmission frequency band of band 4. Therefore, thetransmission signal of band 4 and a harmonic having a frequency that istwo times that of a local oscillation signal used for band 5 receptioninteract with each other and form an in-band interference wave for theband 5 reception signal.

Here, the level of the transmission signal of band 4 is 28 dBm at theoutput terminal of the band 4 power amplifier 710. In addition, theout-of-band suppression of the band pass filters (BPFs) of the duplexers300 is −30 dB, the out-of-band suppression of the low pass filters(LPFs) of the duplexers 300 is −20 dB, the attenuation of the low passfilter (LPF) 720 for band 5 is −30 dB, the out-of-band attenuation ofthe diplexer 320 is −30 dB, the attenuation when the switches of theswitch circuit 310 are on is 0 dB, the attenuation when the switches areoff is −20 dB and the attenuation caused by signal transmission betweenterminals of the power amplification module 700 is −30 dB.

Under these assumptions, the effect of a band 4 transmission signal onthe reception circuit 730 will be described.

First, a signal path A illustrated in FIG. 7 will be considered. Thetransmission signal passes through the band 4 transmission band passfilter (BPF) and the switch with an attenuation of 0 dB. Next, thetransmission signal is attenuated by −30 dB by the diplexer 320. Then,the transmission signal is attenuated by −30 dB by the band 5 low passfilter (LPF) 720. Since the switch for band 5 is on, the transmissionsignal passes through the switch with an attenuation of 0 dB. Inaddition, the transmission signal is attenuated by −30 dB by the band 5reception band pass filter (BPF). Thus, the transmission signal that haspassed along the signal path A acts as an in-band interference signal of−62 dBm at the input of the band 5 reception circuit 730.

Next, a signal path B illustrated in FIG. 7 will be considered. The band4 transmission signal is transmitted to the output terminal of the GSMHB power amplifier 711 with an attenuation of −30 dB. The frequency ofthe transmission signal is inside the band of the GSM HB transmissionlow pass filter (LPF). Consequently, the transmission signal passesthrough the GSM HB transmission low pass filter (LPF) with anattenuation of 0 dB. Next, the transmission signal is attenuated by −20dB by the switch that is in an off state. In addition, the transmissionsignal is attenuated by −30 dB by the diplexer 320. Then, thetransmission signal is attenuated by −30 dB by the band 5 low passfilter (LPF) 720. Since the switch for band 5 is on, the transmissionsignal passes through the switch with an attenuation of 0 dB. Inaddition, the transmission signal is attenuated by −30 dB by the band 5reception band pass filter (BPF). Thus, the transmission signal that haspassed along the signal path B acts an in-band interference signal of−112 dBm at the input of the band 5 reception circuit 730.

Next, a signal path C illustrated in FIG. 7 will be considered. The band4 transmission signal is transmitted to the output terminal of the GSMLB power amplifier 712 with an attenuation of −30 dB. The transmissionsignal is attenuated by −20 dB by the GSM LB transmission low passfilter (LPF). Next, the transmission signal is attenuated by −20 dB bythe switch that is in an off state. Then, the transmission signal isattenuated by −30 dB by the band 5 reception band pass filter (BPF) 720and does not pass though the diplexer 320. Since the switch for band 5is on, the transmission signal passes through the switch with anattenuation of 0 dB. In addition, the transmission signal is attenuatedby −30 dB by the band 5 reception band pass filter (BPF). Thus, thetransmission signal that has passed along the signal path C acts as anin-band interference signal of −102 dBm at the input of the band 5reception circuit 730.

Finally, a signal path D illustrated in FIG. 7 will be considered. Theband 4 transmission signal is transmitted to the output terminal of theband 5 power amplifier 713 with an attenuation of −30 dB. Thetransmission signal is attenuated by −30 dB by the band 5 transmissionband pass filter (BPF). Then, the transmission signal is attenuated by−30 dB by the band 5 reception band pass filter (BPF) and does not passthough the band 5 switch. Thus, the transmission signal that has passedalong the signal path D acts as an in-band interference signal of −62dBm at the input of the band 5 reception circuit 730.

According to the results illustrated in FIG. 7, the output terminal ofthe band 5 (LB) power amplifier 713 is highly sensitive to coupling withthe output terminal of the band 4 (HB) power amplifier 710. Therefore,it is necessary that the characteristics of isolation from the 3G/4G HBpower amplifier be improved for the 3G/4G LB power amplifier.

On the other hand, the effect of coupling of the band (HB) outputterminal and the GSM HB or GSM LB output terminal (path B or path C) issmall compared with the effect from the band 4 transmission signal path(path A). Therefore, the necessity of strengthening the isolation of the3G/4G HB power amplifier, the GSM HB power amplifier and the GSM LBpower amplifier is comparatively low.

The descriptions of FIG. 4A, FIG. 4B, FIG. 5, FIG. 6 and FIG. 7 aresummarized hereafter.

First, as illustrated in FIG. 5, a combination of frequency bands havinga possibility of the reception signal affected by DLCA is LB and VHB orLB and HB. Therefore, for example, a configuration can be considered inwhich a 3G/4G VHB power amplifier, a 3G/4G HB power amplifier and a GSMHB power amplifier form one power amplification module and a 3G/4G LBpower amplifier and a GSM LB power amplifier form another poweramplification module.

Next, as illustrated in FIG. 6, it is preferable that the GSM HB poweramplifier and the 3G/4G LB power amplifier be provided in separatemodules in order to strengthen their isolation from each other.

In addition, as illustrated in FIG. 7, it is preferable that the 3G/4GHB power amplifier and the 3G/4G LB power amplifier be provided inseparate modules in order to strengthen their isolation from each other.The necessity of strengthening the isolation of the 3G/4G HB poweramplifier, the GSM HB power amplifier and the GSM LB power amplifier iscomparatively low.

Taking the above into consideration, in this embodiment, as illustratedin FIG. 2, the 3G/4G VHB power amplifier 200A, the 3G/4G HB poweramplifier 200B, the GSM HB power amplifier 200C and the GSM LB poweramplifier 200D are provided as one power amplification module 130, andthe 3G/4G LB power amplifier 140 is provided as another poweramplification module 140.

If we were to consider only the strengthening of isolation, it would bepreferable to mount the GSM LB power amplifier 200D in the poweramplification module 140 rather than in the power amplification module130. However, if the GSM LB power amplifier 200D were mounted in thepower amplification module 140, a circuit similar to the bias currentconverting circuit 231 would be required in the power amplificationmodule 140 as well in order to generate a GSM bias current.Consequently, if the GSM LB power amplifier 200D were mounted in thepower amplification module 140, the circuit scale of the entirecommunication unit 100 would be increased. As illustrated in FIG. 7, thenecessity of strengthening isolation is comparatively low for the GSM LBpower amplifier 200D. Therefore, by adopting the configuration describedin this embodiment, as well as it being possible to suppress a reductionin reception sensitivity that occurs when DLCA is performed, it is alsopossible to suppress an increase in circuit scale. Thus, it is possibleto provide the multi-mode multi-band communication unit 100 that issuitable for DLCA.

In addition, in the power amplification module 130, a TDD B40/B41transmission signal can be amplified by the 3G/4G VHB power amplifier200A. Furthermore, in the power amplification module 130, the path of aTDD B40/B41 transmission/reception signal can be switched by the switchcircuit 220A. Thus, a TDD operation can be integrated into the poweramplification module 130 and control of the communication unit 100 canbe simplified.

Similarly, in the power amplification module 130, a

TDD B34/B39 transmission signal can be amplified by the 3G/4G HB poweramplifier 200B. Furthermore, in the power amplification module 130, thepath of a TDD B34/B39 transmission/reception signal can be switched bythe switch circuit 220B. Thus, a TDD operation can be integrated intothe power amplification module 130 and control of the communication unit100 can be simplified.

The power amplification module 130 may have a configuration that doesnot support TDD. In addition, the configuration of the input/outputterminals of the power amplification modules 130 and 140 is not limitedto that described above. For example, signals input from the poweramplification module 130 may be supplied to a power amplifier inside thepower amplification module 140 via an output terminal of the poweramplification module 130 and an input terminal of power amplificationmodule 140. Similarly, signals input from the power amplification module140 may be supplied to a power amplifier inside the power amplificationmodule 130 via an output terminal of the power amplification module 140and an input terminal of power amplification module 130.

The purpose of the embodiments described above is to enable easyunderstanding of the present disclosure and the embodiments are not tobe interpreted as limiting the present disclosure. The presentdisclosure can be modified or improved without departing from the gistof the disclosure and equivalents to the present disclosure are alsoincluded in the present disclosure. In other words, appropriate designmodifications made to the embodiments by one skilled in the art areincluded in the scope of the present disclosure so long as themodifications have the characteristics of the present disclosure. Forexample, the elements included in the embodiments and the arrangements,materials, conditions, shapes, sizes and so forth of the elements arenot limited to those exemplified in the embodiments and can beappropriately changed. In addition, the elements included in theembodiments can be combined as much as technically possible and suchcombined elements are also included in the scope of the presentdisclosure so long as the combined elements have the characteristics ofthe present disclosure.

While preferred embodiments of the disclosure have been described above,it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the disclosure. The scope of the disclosure, therefore, isto be determined solely by the following claims.

What is claimed is:
 1. A communication unit comprising: first and secondpower amplification modules, each of the first and second poweramplification modules being integrated so as to be separate from eachother; wherein the first power amplification module includes a firstpower amplifier amplifying a first transmission signal of firstfrequency band in a first communication scheme, a second power amplifieramplifying a second transmission signal of a second frequency band inthe first communication scheme, wherein the second frequency band islower than the first frequency band, a third power amplifier amplifyinga third transmission signal of a third frequency band in a secondcommunication scheme, a fourth power amplifier amplifying a fourthtransmission signal of a fourth frequency band in the secondcommunication scheme, wherein the fourth frequency band is lower thanthe third frequency band, a first bias current generating circuitgenerating a first bias current supplied to the first and second poweramplifiers, and a bias current converting circuit converting the firstbias current into a second bias current supplied to the third and fourthpower amplifiers, the second power amplification module includes a fifthpower amplifier amplifying a fifth transmission signal of a fifthfrequency band in the first communication scheme, wherein the fifthfrequency band is lower than the second frequency band, and a secondbias current generating circuit generating a third bias current suppliedto the fifth power amplifier, and an integer multiple of a transmissionfrequency in the fifth frequency band is substantially equal to areception frequency in any of the first to third frequency bands, or areciprocal of an integer multiple of a transmission frequency in any ofthe first to third frequency bands is substantially equal to a receptionfrequency in the fifth frequency band.
 2. The communication unitaccording to claim 1, wherein the first power amplifier is configured toamplify a sixth transmission signal of the first frequency band in atime division duplexing communication scheme, and the first poweramplification module further includes a first transmission/receptionterminal, wherein the amplified sixth transmission signal is output fromthe first transmission/reception terminal or a first reception signal ofthe first frequency band in the time division duplexing communicationscheme is input to the first transmission/reception terminal, a firstoutput terminal for outputting the first reception signal input from thefirst transmission/reception terminal to a first reception circuit, anda first switch circuit connecting the first transmission/receptionterminal to an output of the first power amplifier or to the firstoutput terminal.
 3. The communication unit according to claim 1, whereinthe second power amplifier is configured to amplify a seventhtransmission signal of the second frequency band in the time divisionduplexing communication scheme, and the first power amplification modulefurther includes a second transmission/reception terminal, wherein theamplified seventh transmission signal is output from the secondtransmission/reception terminal or a second reception signal of thesecond frequency band in the time division duplexing communicationscheme is input to the second transmission/reception terminal, a secondoutput terminal for outputting the second reception signal input fromthe second transmission/reception terminal to a second receptioncircuit, and a second switch circuit connecting the secondtransmission/reception terminal to an output of the second poweramplifier or to the second output terminal.
 4. The communication unitaccording to claim 2, wherein the second power amplifier is configuredto amplify a seventh transmission signal of the second frequency band inthe time division duplexing communication scheme, and the first poweramplification module further includes a second transmission/receptionterminal, wherein the amplified seventh transmission signal is outputfrom the second transmission/reception terminal or a second receptionsignal of the second frequency band in the time division duplexingcommunication scheme is input to the second transmission/receptionterminal, a second output terminal for outputting the second receptionsignal input from the second transmission/reception terminal to a secondreception circuit, and a second switch circuit connecting the secondtransmission/reception terminal to an output of the second poweramplifier or to the second output terminal.
 5. The communication unitaccording to claim 1, wherein the communication unit supports down-linkcarrier aggregation.
 6. The communication unit according to claim 2,wherein the communication unit supports down-link carrier aggregation.7. The communication unit according to claim 3, wherein thecommunication unit supports down-link carrier aggregation.
 8. Thecommunication unit according to claim 4, wherein the communication unitsupports down-link carrier aggregation.
 9. The communication unitaccording to claim 1, wherein the first power amplification moduleamplifies RF signals of a 3G/4G 2.5 GHz band, a 3G/4G 2 GHz band, a 2G 2GHz band and a 2G 1 GHz band, wherein the second power amplificationmodule amplifies RF signals of a 3G/4G 1 GHz band.
 10. The communicationunit according to claim 2, wherein the first power amplification moduleamplifies RF singals of a 3G/4G 2.5 GHz band, a 3G/4G 2 GHz band, a 2G 2GHz band and a 2G 1 GHz band. wherein the second power amplificationmodule ampliries RF signals of a 3G/4G 1 GHz band.
 11. The communicationunit according to claim 3, wherein the first power amplification moduleamplifies RF singals of a 3G/4G 2.5 GHz band, a 3G/4G 2 GHz band, a 2G 2GHz band and a 2G 1 GHz band. wherein the second power amplificationmodule ampliries RF signals of a 3G/4G 1 GHz band.
 12. The communicationunit according to claim 4, wherein the first power amplification moduleamplifies RF singals of a 3G/4G 2.5 GHz band, a 3G/4G 2 GHz band, a 2G 2GHz band and a 2G 1 GHz band. wherein the second power amplificationmodule ampliries RF signals of a 3G/4G 1 GHz band.